Heat curable compositions containing sulfonium salts

ABSTRACT

Heat curable compositions are provided comprising cationically polymerizable organic materials such as epoxy resins, vinyl ethers or phenol formaldehyde resins and thermal curing agents, based on the use of certain aryl sulfonium salts with an organic oxidant, such as an organic peroxide, azonitriles, etc. The heat curable compositions can be used as injection molding compounds or as a coating composition.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending application Ser.No. 11,102, filed Feb. 12, 1979 now U.S. Pat. No. 4,230,814. Relatedapplications are Ser. No. 11,101, for Curable Organic ResinCompositions, Foaming Method and Organic Foams, filed Feb. 12, 1979, nowU.S. Pat. No. 4,241,204 Ser. No. 962,997 filed Nov. 22, 1978, nowabandoned, for Curable Organic Resin Compositions and Foaming Method,which is a continuation-in-part of Ser. no. 861,127, filed Dec. 16,1977, now abandoned, for Curable Organic Resin Compositions and FoamingMethod, U.S. Pat. No. 4,173,551, for Heat Curable Compositions, which isa continuation-in-part of Ser. No. 781,785, filed Mar. 28, 1977, forHeat Curable Epoxy Compositions and Method for Curing Same, nowabandoned, U.S. Pat. No. 4,216,288, for Heat Curable Compositions andMethod for Curing Same which is a continuation-in-part of applicationSer. No. 841,351, filed Oct. 12, 1977, now abandoned, for Heat CurableCompositions, which is a continuation-in-part of Ser. No. 689,247, filedMay 24, 1976, for Epoxy Compositions and Method of Curing Same, nowabandoned, where all of the aforesaid applications are assigned to thesame assignee as the present invention.

BACKGROUND OF THE INVENTION

The present invention relates to heat curable compositions comprising acationically polymerizable organic material, for example, an epoxyresin, a dialkyl hydroxyarylsulfonium salt and an organic oxidant.

As shown in my U.S. Pat. No. 4,216,288, organic resins, for example,epoxy resins can be thermally cured by using an effective amount of anaromatic onium salt such as an aryl iodonium salt and a reducing agent,for example, a thiophenol. The present invention is based on thediscovery that such organic resin also can be thermally cured with anorganic oxidant, such as an organic peroxide in combination with aneffective amount of certain hydroxyaryldialkyl sulfonium salts, forexample, ##STR1## dimethyl-4-hydroxy-3,5-dimethylphenyl sulfoniumhexafluoroarsenate.

STATEMENT OF THE INVENTION

There is provided by the present invention, heat curable compositionscomprising

(A) a cationically polymerizable organic material,

(B) an effective amount of a thermal curing agent consisting essentiallyof an organic oxidant and a dialkyl hydroxyarylsulfonium salt.

Included by the dialkylhydroxyarylsulfonium salts which can be used inthe practice of the present invention are compounds having the formula,

    [R(R.sup.1).sub.a S].sup.+ [Y].sup.-,                      (1)

where R is a C.sub.(6-20) aromatic radical having from 1 to 3 nuclearlybonded hydroxy radicals, R¹ can be the same or different C.sub.(1-8)alkyl radical or an alkylene radical capable of forming a cycloaliphaticor heterocyclic ring, Y is a non-nucleophilic anion, a is an integerequal to 1 or 2, and when R¹ is alkyl, a is 2, and when R¹ is alkylene,a is 1.

Radicals included by R of formula (1) are, for example, ##STR2## R¹radicals include CH₃ --,--C₄ H₉ --, C₂ H₅ --, CH₃ O--, (CH₃)₃ C--, C₆ H₅CH₂ --,--(CH₂)₄ --, --(CH₂)₅ --, --CH₂ --CH₂ --O--CH₂ --CH₂ --, --CH₂--CH₂ --S--CH₂ --CH₂ --, etc.

Preferably, the salts included by formula (1), are ##STR3## where R¹, M,Q and d are as previously defined, and R² -R⁶ are monovalent radicalsselected from hydrogen, C.sub.(1-8) alkyl, C.sub.(1-8) alkoxy, nitro,chloro, etc.

Dialkyl hydroxyphenylsulfonium salts included by formulas (1) and (2)are, ##STR4##

Methods for making some of the dialkyl hydroxy aryl sulfonium salts offormulas (1) and (2) are shown in U.S. Pat. Nos. 4,058,400, 4,058,401and 4,161,478 and Ser. No. 954,196, filed Oct. 24, 1978, now abandoned.

Organic oxidants which can be used in the practice of the inventionincombination with the dialkylhydroxy arylsulfonium salts of formulas 1and 2 to effect the cure of the cationically polymerizable organicmaterial are, for example, organic peroxides such as ketone peroxides,peroxy acids, dibasic acid peroxides, aldehyde peroxides, alkylperoxides, hydroperoxides, alkyl peroxyesters, diperoxide derivatives,for example, t-butyl peroxypivalate, 2,4-dichlorobenzoyl peroxide,caprylyl peroxide, lauroyl peroxide, decanoyl peroxide, propionylperoxide, acetyl peroxide, t-butyl peroxyisobutyrate, p-chlorobenzoylperoxide, benzoyl peroxide, hydroxyheptyl peroxide, cyclohexanoneperoxides, 2,5-dimethylhexyl-2,5-di(peroxybenzoate), di-t-butyldiperphthalate, t-butyl peracetate, t-butyl-perbenzoate, dicumylperoxide, 2,5-dimethyl-2,5-di(t-butyl-peroxy)hexane, t-butylhydroperoxide, di-t-butyl peroxide, methyl ethyl ketone peroxide,p-methane hydroperoxide, cumene hydroperoxide,2,5-dimethylhexyl-2,5-dihydroperoxide, t-butyl hydroperoxide, peraceticacid, perbenzoic acid, m-chloroperbenzoic acid, etc.

In addition to organic peroxides, organic oxidants which also can beused in the practice of the invention include azo-bis alkyl nitriles andother azo compounds, such as ##STR5## iodoso aromatic compounds, such asiodosobenzene, 4-nitroiodosobenzene, iodosobenzene diacetate,4,chloroiodosobenzene, 4-methoxyiodosobenzene, 4-iodosobiphenyl,2-chloroiodosobenzene diacetate, etc.

Cationically polymerizable organic materials which can be used to makethe heat curable compositions of the present invention include epoxyresins, thermosetting organic condensation resins of formaldehyde, vinylorganic prepolymers, cyclic ethers, etc.

The term "epoxy resin" as utilized in the description of thecationically polymerizable compositions of the present invention,includes any monomeric, dimeric or oligomeric or polymeric epoxymaterial containing one or a plurality of epoxy functional groups. Forexample, those resins which result from the reaction of bisphenol-A(4,4'-isopropylidenediphenol) and epichlorohydrin, or by the reaction oflow molecular weight phenol formaldehyde resin (Novolak resin) withepichlorohydrin, can be used alone or in combination with an epoxycontaining compound as a reactive diluent. Such diluents as phenylglycidyl ether, 4-vinylcyclohexene dioxide, limonene dioxide,1,2-cyclohexene oxide, glycidyl acrylate, glycidyl methacrylate, styreneoxide, allyl glycidyl ether, etc., may be added as viscosity modifyingagents.

In addition, the range of these compounds can be extended to includepolymeric materials containing terminal or pendant epoxy groups.Examples of these compounds are vinyl copolymers containing glycidylacrylate or methacrylate as one of the comonomers. Other classes ofepoxy containing polymers amenable to cure using the above catalysts areepoxy-siloxane resins, epoxy-polyurethanes and epoxy-polyesters. Suchpolymers usually have epoxy functional groups at the ends of theirchains. Epoxy-siloxane resins and method for making are moreparticularly shown by E. P. Pleuddemann and G. Fanger, J. Am. Chem. Soc.802632-5 (1959). As described in the literature, epoxy resins can alsobe modified in a number of standard ways such as reaction with amines,carboxylic acids, thiols, phenols, alcohols, etc., as shown in U.S. Pat.Nos. 2,935,488; 3,235,620; 3,369,055, 3,379,653; 3,398,211, 3,403,199;3,563,840; 3,567,797; 3,677,995; etc. Further coreactants which can beused with epoxy resins are hydroxy terminated flexibilizers such ashydroxyl terminated polyethers, hydroxy terminated polyesters, etc.,shown in the Encyclopedia of Polymer Science and Technology, Vol. 6,1967, Interscience Publishers, New York, pp. 209-271 and particularly p.238.

Included by the thermosetting organic condensation resins offormaldehyde which can be used in the practice of the present inventionare, for example, urea type resins, such as

    [CH.sub.2 ═N-CONH.sub.2 ].sub.x.H.sub.2 O

    [CH.sub.2 ═NCONH.sub.2 ].sub.x CH.sub.3 COOH

    [CH.sub.2 ═NCONHCH.sub.2 NHCONHCH.sub.2 OH].sub.2 ;

phenol-formaldehyde type resin, such as ##STR6## where x and n areintegers having a value of 1 or greater; ##STR7## alkoxy silanes havingthe formula,

    (R.sup.7 O).sub.m Si(R.sup.8).sub.n,

where R⁷ is a C.sub.(1-7) alkyl radical, R⁸ is selected from R⁷ radicalsand C.sub.(6-13) aryl radicals and halogenated derivatives, m is aninteger equal to 1 to 4, n is an integer equal to 0 to 3 inclusive andm+n is equal to 4.

In addition, there can be used melamine thiourea resins, melamine, orurea aldehyde resins, cresol-formaldehyde resins and combinations withother carboxy, hydroxyl, amino and mercapto containing resins, such aspolyesters, alkyds and polysulfides.

Some of the vinyl organic prepolymers which can be used to make thepolymerizable compositions of the present invention are, for example, C₂═CH--O--(CH₂ --CH₂ O)_(n') --CH═CH₂, where n' is a positive integerhaving a value up to about 1000 or higher; multi-functional vinylethers,such as 1,2,3-propane trivinylether, trimethylolpropane trivinylether,prepolymers having the formula, ##STR8## and low molecular weightpolybutadiene having a viscosity of from 200 to 10,000 centipoises at25° C., etc. Products resulting from the cure of such compositions canbe used as printing inks and other applications typical of thermosettingresins.

A further category of the organic materials which can be used to makethe polymerizable compositions are cyclic ethers which are convertibleto thermoplastics. Included by such cyclic ethers are, for example,oxetanes such as 3,3-bis-chloromethyloxetane, alkoxyoxetanes as shown bySchroeter U.S. Pat. No. 3,673,216, assigned to the same assignee as thepresent invention; oxolanes such as tetrahydrofuran, oxepanes, oxygencontaining spiro compounds, trioxane, dioxolane, etc.

In addition to cyclic ethers there are also included cyclic esters suchas β-lactones, for example propiolactone, cyclic amines, such as1,3,3-trimethyl-azetidine and organosilicone cyclics, for example,materials included by the formula, ##STR9## where R" can be the same ordifferent monovalent organic radical such as methyl or phenyl and p isan integer equal to 3 to 8 inclusive. An example of an organosiliconcyclic is hexamethyl trisiloxane, octamethyl tetrasiloxane, etc. Theproducts made in accordance with the present invention are highmolecular weight oils and gums.

The heat curable compositions of the present invention can be made byblending the cationically polymerizable organic material with aneffective amount of the thermal curing agent. There can be used 0.1 to10 percent by weight of the dialkyl hydroxyarylsulfonium salt based onthe weight of cationically polymerizable organic material. With respectto the combination of organic oxidant and dialkylhydroxyarylsulfoniumsalt, there can be used from 1 to 100 parts of organic oxidant, per partof dialkyl hydroxy arylsulfonium salt.

The resulting curable composition can be in the form of a varnish havinga viscosity of from 1 to 100,000 centipoises at 25° C. or a free flowingpowder, depending upon the nature of the cationically polymerizableorganic material. The curable compositions can be applied to a varietyof substrates by conventional means and cured to the tack-free statewithin 0.5 to 20 minutes, depending upon the temperature employed.

In certain instances, an organic solvent, such as nitromethane,acetonitrile, can be used to facilitate the mixing of variousingredients. The dialkyl hydroxy arylsulfonium salts can be formed insitu if desired. In addition, the curable compositions may containinactive ingredients, such as silica, talc, clay, glass fibers,extenders, hydrated alumina, carbon fiber process aids, etc., in amountsof up to 500 parts of filler per 100 parts of cationically polymerizableorganic material. The curable compositions can be applied to suchsubstrates as metal, rubber, plastic, molded parts or films, paper,wood, glass, cloth, concrete, ceramic, etc.

Some of the applications in which the curable compositions of thepresent invention can be used are, for example, protective, decorativeand insulating coatings, potting compounds, printing inks, sealants,adhesives, molding compounds, wire insulation, textile coatings,laminates, impregnated tapes, varnishes, etc.

In order that those skilled in the art will be better able to practicethe invention, the following examples are given by way of illustrationand not by way of limitation. All parts are by weight.

EXAMPLE 1

A mixture of three parts of dimethyl-4-hydroxy-3,5-dimethoxyphenylsulfonium hexafluoroarsenate, three parts of benzoylperoxide and 94parts of Shell Epon 828, a diglycidyl ether of bisphenol-A, was stirredand heated to 160° C. The mixture gelled and hardened within 2.5minutes.

EXAMPLE 2

The procedure of Example 1 was repeated, except that Celanese SU8, epoxynovolak resin was substituted for the diglycidyl ether bisphenol-A epoxyresin. The resulting heat curable composition required eight minutes toharden at 120° C.

EXAMPLE 3

A series of mixtures were prepared utilizing 100 parts of3,4-epoxycyclohexylmethyl-3,4-epoxy cyclohexane carboxylate, 3 parts ofa hexafluoroantimonate salt of the formula, ##STR10## and 3 parts ofvarious organic oxidants. The mixtures were then heated to 130° C. todetermine gel times. The following results were obtained:

    ______________________________________                                        Organic oxidant       Gel Time                                                ______________________________________                                        None                  >7 min.                                                 benzoyl peroxide      1 min., 30 sec.                                         cumene hydroperoxide  2 min., 50 sec.                                         2,3-dichloro-5,6-dicyano-                                                                           40 sec.                                                 quinone                                                                       azo-bisisobutyronitrile                                                                             6 min. 15 sec.                                          lauroyl peroxide      4 min. 5 sec.                                           ______________________________________                                    

EXAMPLE 4

In accordance with the procedure of Example 3, heat curable mixtureswere prepared utilizing 100 parts of ERL 4221(3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate), 3 parts of##STR11## and 3 parts of various organic oxidants. The mixtures wereheated to 150° C. to determine when the mixtures changed from a fluidcondition to the solid cured state. The following results were obtained:

    ______________________________________                                        Organic oxidant     Gel Time                                                  ______________________________________                                        None                25 min.                                                   methylethyl ketone peroxide                                                                       11 min.                                                   t-butyl hydroperoxide                                                                              3 min.                                                   ______________________________________                                    

EXAMPLE 5

A mixture composed of 100 parts of 1,4-butanediol diglycidyl ether, 3parts of t-butyl hydroperoxide and 3 parts ofdimethyl-3,5-dimethoxy-4-hydroxyphenylsulfonium hexafluoroarsenate washeated at 150° C. The mixture cured to a hard crosslinked resin after 18minutes. The same mixture free of the t-butyl hydroperoxide did not gelafter it was heated for 60 minutes at 140° C.

EXAMPLE 6

Mixtures were prepared having 100 parts of diethyleneglycol divinylether and 3 parts of ##STR12## There was added 3 parts of t-butylhydroperoxide to one of the mixtures. Both mixtures were thoroughlystirred and then heated to 140° C. The mixture containing the peroxidecured after 5 minutes, while the mixture free of peroxide required 15minutes to cure to a tack-free condition.

EXAMPLE 7

Mixtures of 100 parts of Methylon® resin (a phenolformaldehyde resole ofthe General Electric Company) and 3 parts of ##STR13## were thoroughlystirred. There was added 3 parts of t-butyl hydroperoxide to one of themixtures. The mixtures were then heated at 150° C. The mixture havingthe t-butyl hydroperoxide cured to a hard crosslinked insoluble resin.The mixture free of the organic oxidant remained substantiallyunchanged.

In addition to aryl sulfonium salts of formula (1), I have found thatadditional arylsulfonium salts also can be utilized in the practice ofthe present invention to effect the heat cure of cationicallypolymerizable organic material when used in combination with an organicoxidant, such as an organic peroxide as defined above. Thesearylsulfonium salts are included within the formula,

    (R.sup.7).sub.3 SMQ.sub.d,                                 (3)

where R⁷ is a C.sub.(6-13) aromatic organic radical, for example, phenyland halogenated derivatives thereof, or where such arylsulfonium saltsare included within the formula, ##STR14## where R⁸ is selected from R⁷radicals, R⁹ is selected from C.sub.(2-8) alkylene radicals and R¹⁰ isselected from C.sub.(1-8) alkyl radicals, for example, methyl, ethyl,propyl, butyl, etc., and MQ_(d) is as previously defined.

Included within the arylsulfonium salts of formulas (3) and (4) are, forexample, ##STR15##

Methods for making some of the arylsulfonium salts of formulas (3) and(4) are shown in U.S. Pat. Nos. 4,058,400, 4,058,401 and in U.S. Pat.No. 4,161,478, assigned to the same assignee as the present invention.

The curable compositions of the present invention can be made inaccordance with the procedures described in making the heat curablecompositions utilizing dialkyl hydroxy aryl sulfonium salts of formula(1).

EXAMPLE 8

To a mixture of 94 parts of Ciba Geigy CY 179 and 3 parts by weight of##STR16## there was added 3 parts of an organic peroxide. The mixturewas heated to 130° C. The following gel times were measured:

    ______________________________________                                        Peroxide           Gel (cure) time (min)                                      ______________________________________                                          --               >6.5 min                                                   dicumyl peroxide   4.5 min                                                    cumene hydroperoxide                                                                             3.5 min                                                    lauroyl peroxide   4.1 min                                                    azobisisobutyronitrile                                                                           6.5 min                                                    benzoyl peroxide   1.5 min                                                    ______________________________________                                    

EXAMPLE 9

A mixture composed of 95 parts Epon 828, 2 parts triphenylsulfoniumhexafluoroantimonate and 3 parts benzoyl peroxide were heated rapidly(at 20° per minute) from 25° C. to 300° C. During the heating period,cure was observed by recording the heat of polymerization using adifferential scanning calorimeter. When the peroxide was omitted, noheat or cure was observed.

Although the above examples are directed to only a few of the very manyheat curable compositions included by the present invention, it shouldbe understood that the present invention includes a much broader classof heat curable materials as shown by the description preceding theseexamples.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:
 1. Heat curable compositions comprising(A) a cationicallypolymerizable organic material (B) an effective amount of a thermalcuring agent consisting essentially of an organic oxidant and an arylsulfonium salt selected from the class consisting of a triarylsulfoniumsalt and an aryl acyl dialkyl sulfonium salt.
 2. A heat curablecomposition in accordance with claim 1, where the triarylsulfonium saltis a triphenylsulfonium salt.
 3. A heat curable composition inaccordance with claim 1, where the triarylsulfonium salt istriphenylsulfonium hexafluoro phosphate.
 4. A heat curable compositionin accordance with claim 1, wherein the aryl acyl dialkyl sulfonium saltis phenacyl dimethylsulfonium salt.
 5. A heat curable composition inaccordance with claim 1, where the aryl acyl dialkyl sulfonium salt is aphenacyl dimethylhexafluorophosphate.
 6. A heat curable composition inaccordance with claim 1, wherein the cationically polymerizable organicmaterial is an epoxy resin.
 7. A heat curable composition in accordancewith claim 1, where the cationically polymerizable organic material is avinyl ether.
 8. A heat curable composition in accordance with claim 1,where the cationically polymerizable organic material is a phenolformaldehyde resin.
 9. A heat curable composition in accordance withclaim 1, wherein the organic oxidant is an organic peroxide.
 10. A heatcurable composition in accordance with claim 1, where the organicoxidant is benzoylperoxide.